Current high performance signal processing techniques require that the data be in digital form. However, analog data coming, for example, from a wide variety of acoustic, optic, or electromagnetic sensors may exceed the conversion rates or precision of present day analog to digital converters and thus prevent or impede the real time processing of such data for meaningful results. As the need for more sophisticated data handling for improved sensitivity, precision, resolution, range, or the like materializes, data generation, conversion and/or handling capabilities often are exceeded. For example, the precision and data rates of analog to digital converters often are inadequate as are the switching times of interconnected processing circuitries.
Two (of numerous) methods by which a high speed analog to digital conversion can be effected are known as the flash method and the successive approximation method. Of the two, the faster method is the flash method which requires a number of comparators equal to 2.sup.n -1 where n is the number of bits to be resolved. This technique in current practice is limited to 8-10 bits of resolution. The other method, binary successive approximation, is an analog to digital conversion technique that uses only a single comparator but requires n successive comparisons for n bit analog to digital conversion. A limitation of this technique is that it is significantly slower, on the order of a factor of n when compared to the flash method of analog to digital conversion, assuming that both use the same circuit technology. However, even when these two methods are considered, the presently available analog to digital converters do not have sufficient speed to permit high precision or wide dynamic range analog-to-digital conversion at the Nyquist rate or do not have a sufficient resolution to permit the application of modern signal processing techniques such as minimum variance distortionless look beamforming or eigenvector based direction finding.
Thus, there exists in the art a continuing need for improvements in analog to digital converter speed and resolution or dynamic range which would allow greater precision in the processing of received signals.